The paper, by John McLean, Professor Chris de Freitas and Professor Bob Carter, showed that the Southern Oscillation Index (SOI), a measure of El Nino-Southern Oscillation (ENSO) conditions, is a very good indicator of average global atmospheric temperatures approximately seven months ahead, except when volcanic eruptions cause short-term cooling.

The lead author, McLean, points to a fall in temperatures that began in October last year, seven months after the abrupt shift to La Nina conditions, and according to last month's data is still continuing.

"The delayed response is important for two reasons." McLean says, "Firstly the high annual average temperature in 2010 was due to the El Nino that ended around March but whose delayed effect on temperature continued until late in the year. Secondly it means that the ENSO conditions can be used to predict with reasonable confidence the average global temperatures up to seven months ahead."Several previous scientific papers have discussed the delayed response, including two by critics of McLean's paper. Although the other papers used different data sources they came to similar conclusions about the delay.

The key question is how much influence the ENSO has on average global temperature. McLean says that this is difficult to determine, because both can be affected by short-term events such as wind, clouds and tropical storms, but the sustained close relationship in the data of the last 50 years shows the influence is significant.

"The historical data also casts serious doubt on the hypothesis that carbon dioxide causes dangerous global warming," says McLean. "Since 1958 there's been a 30% increase in atmospheric carbon dioxide and if this had a major influence on temperature we'd expect to see clear evidence of the temperature continually rising above what the SOI suggests it should be, but this is not happening".

The Bureau of Meteorology reports that ENSO models currently indicate that the La Nina will be with us well into autumn and fade slowly to neutral conditions by June. Taking into account the seven-month time lag it is likely that 2011 will be the coolest year since 1956 or even earlier, McLean says.

He also says that records show the oceans absorb more carbon dioxide during a La Nina event than during an El Nino, which means that the increase in atmospheric carbon dioxide in 2011 is likely to be less than in recent years.

ENDS

Nature defeats UN's climate body, yet again

McLean, Carter and de Freitas published their landmark paper in 2009. It provides scientific proof that global atmospheric temperature rises and falls with the Southern Oscillation (El Nino, La Nina).

The UN's climate body became worried. Leaked Climategate scandal e-mails advocated conspiring to knock out the paper by any means. Scientific publishing guidelines were breached trying to knock it out.